 Six string quartets by Mozart are dedicated to Haydn (K. 387, 421, 428, 458, 464, 465), the "Haydn" Quartets.Haydn was already a fairly well-known young composer in Mozart's childhood.His six string quartets Opus 20 (1772), called the "Sun" Quartets from the drawing of the sun on the cover of the first edition, were widely circulated and are conjectured (for instance, by Charles Rosen) to have been the inspiration for the six early string quartets K. 168–173 the 17-year-old Mozart wrote during a 1773 visit to Vienna.